G. N. Komarov, “Spectral problems with boundary and conjugating conditions depending on a parameter”, Ukr. Mat. Zhurn., vol. 47, no. 12, pp. 1653–1660, Dec. 1995, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5558